I use both on my devices, there are a few differences. You can't print from OneDrive itself, you have to open the file in another app (printer app), while GDrive allows airprinting and Google Cloud printing, e.g.
I also have Box (loads of online storage space) and Dropbox on my iPads. Each one is used for it's own purpose.
Afaik they are all free, so take a look at them, try them, and then decide which one to use - or use them all.